Combustion heating apparatus and controls therefor



F. B. AU BERT Oct. 11, 1949.

COMBUSTION HEATING APPARATUS AND CONTROLS THEREFOR Filed July 26, 1943 6 Sheets-Sheet 1 INVENTOR 3M 6. W

ATTORNE;

F. B. AUBERT Oct. 11, 1949.

COMBUSTION HEATING APPARATUS AND CONTROLS THEREFOR 6 Sheets-Sheet 2 Filed July 26, 1943 w E F INVENTOR 56:14, 6%; BY

PWKM

ATTORNEY Oct. 11, 1949.

F. AUBERT COMBUSTION HEATING APPARATUS AND CONTROLS THEREFOR Filed July 26, 1943 6 Sheets-Sheet 3 INVENTOR 5M 6. W

Oct. 11, 1949. F. B. AUBERT 2,484-602 COMBUSTION HEATING APPARATUS AND CONTROLS THEREFOR Filed July 26, 1943 6 Sheets-Sheet 4 M ATTORNEY Oct. 11, -1 949.

F. a. AUBERT COMBUSTION HEATING APPARATUS AND CONTROLS THEREFOR Filed July 26, 1943 6 Sheets-Sheet 6 FUEL PUMP INVENTOR M 8. W

W /C M FIG-"l5 M ATTORNEY Patented Oct. 11, 1949 COMBUSTION HEATING APPARATUS AND CONTROLS THEREFOR Fred B. Aubert, Grosae Pointe, Mich.

.ipplioatlon July 28, 1943, Serial No. 496,099 21 Claims. (cl; 158-28) This invention relates to new and useful improvements in heating apparatus and more particularly to the control of burner operation.

An object of the invention is to provide a. heating apparatus which is particularly adapted for the heating of enclosed spaces in aircraft such for example as the cabin or fuselage.

Another object is to provide a control for in-' itiating a burner operating cycle.

Another object is to provide a control by which the supply of fuel is increased upon an increase in the rate of supply of combustion air.

Another object is to provide means assuring operation of the fuel igniting means prior to the supplying of fuel.

Another object is to provide for scavenging of the combustion chamber upon shutdown of the burner.

Another object is to provide a timed control for the heating apparatus.

The invention consists in the improved control system and device, the cooperative relation of parts and their groupment in cooperative relation, to be more fully described hereinafter and the novelty of which will be particularly pointed out and distinctly claimed.

In the accompanying drawings to be taken as a part of this specification there are fully and clearly shown several preferred embodiments of the invention, in which drawings:

Figure 1 is a view in front elevation of a control mechanism casing;

Fig. 2 is a top plan view of the encased mechanism with lead wires broken away for clarity and taken through the casing wall substantially on the line 2-2 of Fig. 1;

Fi 3 is a view in end elevation of the encased mechanism with lead wires broken away for clar ity taken on the line 33 of Fig. 2;

Fig. 4 is a plan view in section of the encased mechanism with lead wires broken away for clarity taken on the line l4 of Fig. 3;

Fig. 5 is a detail view in section on the line 5--5 of Fig. 3;

Fig. 6 is a detail view taken on the line 6-6 of Fig. 3;

Fig. 7 is a detail view of a relay switch and I taken on the line |-1 of Fig. 3;

Fig. 8 is an enlarged perspective view of one. of the switches forming part of the control system;

Fig. 9 is a detail view showing certain switch operating members in burner starting position;

Fig. 10 is a view similar to Fig. 9 but showing the parts at termination of burner ignition;

Fig. 11 is a diagrammatic view of the heating apparatus and control system as applied to the heating of aircraft;

Fig. 12 is a diagrammatic view similar to Fig. 11 but showing another form of control mechanism;

Fig. 13 is a detail diagrammatic view of another form of fuel flow controlling means:

Fig. 14 is a view of the control mechanism and apparatus as in Fig. 1 but having an electric drive for the control mechanism;

Fig. 15 is a diagrammatic view of another form of control system having an electric drive, and

Fig. 16 is a diagrammatic view of a heating apparatus embodying the feature of the foregoing control systems of control of the fuel in accordance with the supply of combustion air as included in the systems of Figs. 11 to 15.

Referring to the drawings by characters of reference, l designates generally a rectangular control mechanism casing having frontand rear end cover or closure members 2, 3 which are secured in position by cover screws 4.

Within the casing there is an L-shaped supporting member having a bottom flange 5 which seats on the bottom casing wall and has an upstanding front flange 6 which is spaced from and rigidly secured by brackets l to the front cover member 2. Positioned between the flange 6 and cover member 2 and secured to the flange 6 by screws 9, there is a hand wound spring driven timing motor 8 which may be of the type known on the market as the Minute Minder, manufactured by the Lux Clock Company, New Haven, Connecticut and which has a combined winding and drive shaft I0 extending from the opposite walls or faces of the clock or timer motor casing. The front end portion of shaft l0 which projects through the cover member 2 has secured thereon a winding key and stop member I I cooperable with posts or stop pins l2, l3 to limit the rotation of the shaft in and unwinding and winding respectively of the clock spring. The inner end of the shaft ill, see Fig. 5, which projects through the flange 6- carries a cam disc or member H to which the shaft is connected for positive driving action bya pin and slot connection IS. A set screw is engaging the shaft I0 and threaded in the hub of the member i4 locks the same against endwise movement on the shaft l0.

Secured on the bottom flange 5, there is a base member I! on which is mounted a U-shaped bracket member l8 having upstanding parallel sides terminating in lateral extending arms l9 and 20 which are apertured to provide aligned bearings co-axial with the shaft it. Journalled in the arm apertures and extending between the arms 15, there isan armature supporting shaft 2| which is held against endwise movement by outward facing shoulders bearing against the arms. The shaft 2| projects through the arm 20 and may extend into a recess in the inner end of the shaft Ill. Secured on the projecting end portion of the shaft 2| there is a cam disc or member 22 held in position by a set screw 23 threaded in the disc hub and locked against the shaft 2|. The hub of dlsc'22 has aslot or recess 24 facing the disc i4 and receiv a the projecting end of a pin 28 which extends from and is fixed in an aperture in the disc i4. The slot 24 is preferably a cylindrical bore having a diameter sufficiently greater than the diameter of the pin 25 as to provide a lost motion connection between the shafts It and 2| for relative movement therebetween. The extent of lost motion is preferably substantially of shaft rotation. Rigidly secured to the shaft 2| and extending longitudinally thereof, there is a substantially rectangular magnetic plate member or armature 26 which has an ear or flange 21 extending into and fitting within a slot in the face of cam disc 22, so that the armature and cam disc are positively locked together. Surrounding the shaft 2| adjacent the arm l8, there is a helical coil spring 28 having one end anchored, as at 29, to the armature 26 and having its other end secured to the arm NJ, as at 30, such that the spring 22 tends to rotate the shaft 2| ina clockwise direction facing Fig. 3. Positioned between the sides of and secured to the face of the bracket ll there is an electro-magnet 3| having lead wires 32, 33 cooperable with the armature 26 to provide a. means for holding the cam disc 22 against rotation. The armature 2i overlies the arms I! and 2D and is limited thereby from engagement with the core of the electro-magnet 2|, so that an air gap of say twenty-five thousandths of an inch will be maintained.

Secured to the inside face of the supporting member flange 6 there are a plurality of switch units, each comprising a housing of electric insulating material secured on studs 24 projecting from the flange 6. These switch units are of the single pole, double throw type actuated by a snap acting spring mechanism 15, operated by a thrust member 36 which projects through an aperture in the housing cover member. Further description of these switches is believed unnecessary as they may be obtained on the market, the type known as the Acro snap switch, manufactured by the Acro Switch Company, Cleveland, bein preferable. Two of these switch units, designated 31, 38, overlie the cam discs I4, 22 and have their thrust members 3!, respectively projecting downward, see Fig. 6. Positioned at opposite sides of the cam disc l4 there are switch units 4|, 42 having thrust members 43, 44 respectively. Also projecting from the rear face of the flange 2 there are rods or shafts 45, 46 positioned above and at the sides of the cam disc I4 and adjacent the underside of the switch units 31, 38. Journalled on the post 45 there m a cam follower lever member 41 extending downward for abutting engagement intermediate its ends with the thrust member 44 and having its free end rebent as at 4| to provide a cam follower portion engaged with the circumferential face of the cam disc l4. The follower member 41 is swung or moved to the left facin Fig. 3 to operate to closed position the switch of unit 42 byacamorlobeflonthecamdisc I4.

0n the rod 48 there is iournalled a cam follower lever member II engageable intermediate its ends with the switch operating thrust member 43 and terminating at its free end in a follower portion 4| engaged with the circumferential face of the cam disc 14. The follower portion 5| operates with a cam or lobe 52 for actuating the double throw switch member of unit 4| by depressing its thrust member 43. Also Journalled on the rod 40 there is a cam follower lever member 53 having a transverse extension 54 engageable with the thrust member 2!, 4. and having its free end terminating in a follower portion 55, riding on the circumferential face of the cam disc 22. The follower portion 55 is cooperable with a cam or lobe 56 on the disc 22 so that the follower member actuates the thrust members 29, 4| to operate the switches of units 21, ll. The cam or lobe 4! extends, facing Figs. 4 and 11, a distance more than 120 and the cam or lobe 52 is spaced from the follower member portion 5| substantially the cam 52 extending clockwise facing Figs. 4 and 11, a distance greater than 30. The cam or lobe 56 is positioned substantially in a clockwise direction from the cam or lob 49.

Positioned on the opposite side of the shaft 2| from the electro-magnet ll there is a relay switch 51 having a magnetic operating coil 58. The switch 51, see Fig. 7, is a unit such as shown in Fig. 8 having an operating thrust member 59 and rigidly clamped in position between the sides of an inverted U-shaped bracket 50. The coil 58 is secured to the base or bottom wall of a U-shaped bracket 6| and is positioned between the sides thereof, the base being secured by rivets or the like to the base of the bracket 60. Positioned in overlying relation to the sides of bracket 5| for engagement therewith to limit its movement, there is a magnetic plate member or armature 82 for attraction by the coil 58. The bracket sides maintain an air gap of say twenty-five thousandths of an inch between the armature 62 and the magnet core. The armature 62 is secured to a shaft 63 which extends between and is journalled in aligned apertures in the sides of the bracket 6|. Supported by one of the bracket sides there is an adjustable stop member 64, such as a screw threaded through a sleeve 65, carried by an arm 65 which overlies the armature 62. The screw 64 is engaged by the armature 62 to limit the upward movement of the armature by a helical coil spring Bl which surrounds the armature shaft 63 and has one end anchored to the armature and the other end secured to the bracket 6|. Supported by the base of the bracket 80, there is a tubular guide member 68 which is aligned with the thrust member 59'and which extends upward to a point adjacent the under- Side of the armature 62. Positioned within and guided for reciprocation by the member 68, there is a. push rod 69 which seats on the thrust member 59 and which, at its upper end, abuts the armature 62 so that the switch 51 will be actuated when the coil 58 is energized.

Clamped in position by the studs 34 and extending horizontally above the shaft 2| there is a supporting bracket 10 which carries a terminal block or jacket 1| having contact fingers electrically engageable with matching sockets in a terminal block or receptacle 12 carried by a mounting panel 13 of electric insulatin material. The panel 13 is mounted on studs 14 secured to the inside face of the casing cover mem ber 3. The jacket terminal A is connected by a lead wire 15 to the fixed contact 16 of the switch 42 which has the contact of its switch blade I'l connected by a lead wire I8 to the switch blade 18 of the double throw switch U. The switch contact 80, normally closed by the contact of blade 18, is connected by a lead wire II to the switch blade 82 of switch 31. A contact of switch blade 82 is cooperable with a fixed switch contact 83, connected to the lead wire 32 oi thecoll II. The lead wire 32 is connected by a lead'wire 84 to the jacket terminal B. Secured to the inside face of the front cover member 2 above the timing motor 8, there is a manually operable normally closed switch 85 which is a unit such as shown in Fig. 8.' The housing for switch 88 is carried by a guide and supportingsleeve 88 secured in an aperture in the member 2 and aligned with the switch blade operating thrust member. Supported and reciprocable in the sleeve 88 there is a thrust member operating push button 81. The fixed contact 88 of the switch 85 is connected to the holding coil 3| by the lead wire 33. The contact of switch blade 88 of switch 85 is connected by a lead wire 80 to the jacket terminal C. The switch 42 has its blade 11 and lead wire 18 connected by a lead wire 8| to the jacket terminal D. The normally open fixed contact 82, ofthe,

switch H is connected by a lead wire 83 to the relay coil 58. From the other terminal of the coil 58 a lead wire 84 connects to the jacket terminal E. The relay switch arm 85 is connected by lead wire 86 to the jacket terminal A and the fixed relay contact 91 is connected bylead wire 88 to the lead wire 8| and switch arm 82 of the switch 31. The switch 38 has its switch arm 88 connected by a lead Wire I to the jacket terminal F. The fixed contact IOI of switch 38 is contor-speed resistor I28 tothe socket terminal 3' for connection to the jacket terminal B. There are two parallel resistor-circuits, one having a low motor speed resistor I23 connectedby a lead wire I24 to the socket terminal B which connects to the jacket terminal B. The other parallel circuit has a high motor speed resistor I25 connected by a lead wire I28 to the socket terminal 0' connected to the jacket terminal G. In the combustion chamber I88 and cooperative with the fuel feed member H3, there is a hot wire ignite: I21 for generating an igniting temperature in excess of 1200 F. The igniting means I2! is connected to ground by a lead wire I28 and has its other end connected by a lead wire I28 to the socket terminal E connected to the Jacket terminal E. An air temperature safety switch I30 has a tem- 1 perature responsive member. I3I in heat exchange relation with the jacket I I0 and operable to open the safety switch at a temperature of say 170 F.

The switch I30 is connected by a lead wire I32 to the socket terminal C connected to the jacket terminal C. The combustion chamber I08 is sup- I plied with combustion supporting air through a nected by a lead wire I02 to the jacket terminal G. A pilot light indicator I03 has one terminal connected by a lead wire I04 to the fixed switch contact I 0| and lead wire I02, the other pilot light terminal being connected to ground by a lead wire I05. A translucent ruby lens I08 is supported in the casing wall above pilot light I03 to indicate from the exterior of the casing that the light is burning. The connectors or terminals of the socket terminal block 12 are connected to the source of current supply and to the heating apparatus.

The fuselage or cabin of the aircraft which is to be heated by the heating apparatus is designated I01. The heating apparatus has a furnace I88 with a combustion chamber I08 having an outlet stack or discharge duct I 08' leading to the exterior of the aircraft. Surrounding the combustion chamber I09 there is an air heating jacket or plenum chamber IIO which is supplied with air to be heated from the exterior of the aircraft through an inlet conduit I I I. The chamber II 0 has a discharge conduit II2 for the heated air and which may lead to one or more desired discharge points. Within the combustion chamber I 09 there is a liquid fuel capillary feeding member I I3 which is supplied with liquid fuel from a constant level device I I4. A constant displacement pump I I5 feeds the device I I 4 through a conduit I I8 and draws liquid fuel from a supply tank I I1. The pump H5 is driven by an electric motor II8 having one terminal connected to ground by a lead wire H8 and having its other terminal connected by a lead wire I20 to one terminal of a pressure responsive safety switch I2I which acts to open the switch I20 upon the occurrence of excess liquid pressure in the conduit IIB. From the other terminal of the safety switch a lead wire I22 connects through a low moduct I33 which is fed with air under pressure by a blower I34 driven by an electric motor I35 or is supplied with air under pressure from an air ram I38 comprising a branch duct leading to the exterior of the airplane. The blower motor I35 has one terminal connected to ground by a lead wire I31 and has its other terminal connected by a lead wire I38 to one fixed terminal I38 of a double throw air pressure responsive switch I40 which is responsive to the air pressure in the duct I33. The air pressure responsive switch arm I is connected by a lead wire I42 to the socket terminal D connected to the jacket terminal D. The normally open fixed contact I43 of the air pressure responsive switch is connected by a lead wire I44 to the socket terminal F connected to the jacket terminal F. The foregoing circuits are energized from a source of electric current supply such as a battery I45 preferably having a potential of 24 v. and which has its negative terminal connected to ground by a lead wire I46 and has its positive terminal connected by lead wire I47 to the socket terminal A connected to the jacket terminal A. The lead wires 84, I00, I02, I24, I26, I28, I32 and I42 extend into the casing I through a tubular conduit member I48 secured in an aperture through the side wall of a casing.

The operation of thecontrol device and heating apparatus of Figs. 1 to 11 is as follows. When it is desired to start the heating apparatus to supply heat to the enclosed aircraft space, the winding knob or key II is rotated clockwise facing armature supporting shaft 2| and their respective cams to set position for burner starting operation. Rotation of shaft I0 first engages cam 48 with follower member 41 to close the main switch 42 and then, upon 90 of continued rotation which covers a 15 minute timer motor running period, engages cam 52 with follower member 50 to actuate the double throw switch M to open the circuit at contact and to close the circuit between blade I8 and contact 82. At the time of closure of switch 42, the lost motion connection by pin 25 and slot 24 has been taken up so that the cam discs I4 and 22 will have simultaneous equal r0- tation. Winding of the shaft I8 continues from the point at which follower member 88 drops 01 of cam 82 for a distance of 30, which is a five minute running interval or period of the motor 8. This additional 30' winding movement of shaft I8 acts to move the cam 58 under the follower member 83, thereby closing the switches 31, 38 and carries or rotates the holding means armature 28 against the force of spring 28 into holding relation to the electro-magnet 3|. The cams and their switch operating follower members and the armature 28 will now be positioned as shown in Fig. 9. Curreht from the battery I45 will now be supplied through panel terminal members A, A and lead wire to the main switch fixed contact 18, thence through switch blade 11 and lead wires 18, 8| to panel terminal members D, D, thence via lead wire I42 to the switch arm I and closed contact I38 of the air pressure or ram switch I48, thence via lead wire I38 to one terminal of the blower motor I35 and thence to ground via lead wire I31. The blower I34 is thus placed in operation to supply combustion air through duct I33 to the combustion chamber I88. Closure of switch 42 also closed the circuit to switch arm 13 of the double throw switch 4| so that circuit is completed from the switch arm to the now closed, but normally open, contact 82 to the relay coil 58 via lead wire 33, thence via lead wire 94 to the panel terminals E, E and via lead wire I28 to the hot wire igniter I21 and thence to ground via lead wire I28. The igniter I21 is therefore energized but closure of the relay switch 51 'to supply fuel is dependent upon a sufficient amperage of the current supply, such as to raise the temperature of the igniter I21 above a minimum desired igniting temperature, as above 'noted. The relay switch 51 will therefore also not be closed if there is a break in the igniter circuit or if the operating amperage for relay coil 88 and igniter I21 is not provided. The closure of switch 51 establishes a circuit from the battery I45 in shunt with the switch 42 and now open, but normally closed, contact 80 of switch 4|. This shunt circuit leads from the battery I45 through lead wire I41 to panel terminals A, A, thence to relay switch arm 95 via lead wire 85 and from relay switch contact 91 via lead wire 98 to the lead wire 8| and switch arm 82 of switch 31. Cam 58 has closed the switch 31 and the circuit will continue through lead wire 32 to the coil of holding magnet 3| and thence via lead wire 33 to the fixed contact 88 of the burner stopping switch 85 and thence from the burner stopping switch contact 89 via lead wire 98 to panel terminals C, C and thence to the bonnet temperature safety switch I38 and to ground. Closure of relay switch 51 also completes the circuit through the low motor speed switch 31 via lead wire 84 (in Fig. 11 lead wires 32 and 84) to panel terminals B, B, thence via lead wire I24 through low motor speed resistor I23 and lead wire |22 to the closed fuel pressure safety switch I2I and thence via lead wire I28 to one terminal of the pump motor 8 and thence to ground via lead wire II8. Fuel and combustion air being supplied and the igniter I21 being at igniting temperature, the heating apparatus will be in operation and the timing motor 8, the winding key II having been released, will also be operating or running to rotate the shaft I8 counterclockwise facing Fig. 1 and clockwise facing Figs. 3, 9 and 10 When the ignition period has elapsed, preferably of five minutes duration, the cam 52 will have released follower member 88 r of switch 4| will move back to inltialpositiomclnsingtheeircuitofoontact 88 of contact 82. The switches, being snap acting, the interchange of circuits from contact 82 to contact 88 will not interfere with burner operation. Breaking of circuit at contact 82 will deenergine the relay coil 88 and the igniter I21, thereby opening the relay switch 81, but the closure of arm 18 with contact 88 will maintain the continued operation of the pump 8, since the contact 88 and the relay switch 51 are in shunt circuit. As long as combustion air pressure in the supply duct I33 and therefore in the branch duct |3 8 is below the pressure for which the ram switch I48 is set, the heating apparatus will continue in operation at low fuel consumption due to low speed pump motor operation which is suillcient to supply fuel in accordance with the air supplied by the blower I34.

When the quantity of air supplied to the combustion chamber through duct I33 exceeds the quantity for a proper fuel air ratio, the increased pressure of the combustion air in the duct I33 and branch duct I88 will actuate the ram switch I48 to make circuit between the arm I and the contact I43. This increased air pressure for actuating the switch I48 will result from the speed of the aircraft in flight. Closure of the circuit between arm I and contact 43 will break the blower motor circuit at switch contact I38 and will complete the high speed fuel pump motor circuit as follows: From contact I43 via lead wire I 44 to the panel terminals F, F, thence via lead wire I88 to switch arm 83 of switch 38 and its engaged contact "I, thence via lead wire I82 to the panel terminals G, G to lead wire I28 and through the high motor speed resistor I25, lead wire I22 and closed fuel pressure switch III to the motor 8 via lead wire I28. Closure of contact between arm I and contact I43 will also complete the circuit through closed switch 38 to the indicator pilot light I83, connected by lead wire I84 to contact "I and lead wire I02 and connected to ground by lead wire I85. As long as the aircraft continues in flight and the air pressure in ducts I83 and I38 is greater than the pressure created by the blower I34, the heating apparatus will continue to operate at high fuel supply.

Irrespective of whether burner is operating at high or low fuel consumption, the operation of the heating apparatus can be stopped by the manual switch 88. when the push button 81 of this switch is moved inward, the switch 85 will be opened by movement of arm 83 out of engagement with contact 88, which will break the circuit through the holding magnet coil 3|. Deenergization of coil 3| will permit the spring 28 to move the armature 28 quickly to the position of Figs. 3 and 11, due to the lost motion of pin 35 in slot 24. Cam 88 will move with initial movement of armature 28 and out from under follower member 83 so that the switches 31 and 38 will be opened, which will break both the low speed and the high speed fuel pump motor circuits. The release of the armature 25 will reinstate and release for continued operation the timing motor 8. Cam disc I4 will now again be rotated clockwise facing Figs. 3, 9 and 11 from its position in Fig. 10. The 90 of cam movement from the position of Fig. 10 occupies a time period of 15 minutes and when this time period or interval has elapsed, the cam 48 will move out from under the follower member 41 so that the 9 switch arm 11 of switch 42 will break circuit with the contact member 16, thereby breaking the circuit to the ram switch arm I. If the aircraft is on the ground or its air speed has decreased, so that the ram switch I40 breaks ciragoo.

via lead wire m to the motor 222 oi' the combustion air blower 233 and to ground via lead wire 234." Closure of'main switch 204 also completes the circuitto the coil as of relay switch 225 and a predetermined period of supply of scavenging air to the combustion chamber I09 immediatelyfollowing the stopping of the fuel pump H5.

It will be apparent that if the pump I I5 is stopped during flight by operation of switch 85,. that,

scavenging air will be supplied by the speed of the aircraft through branch duct I36 and the blower motor I35 will not be placed in operation, but if the pressure of the combustion air decreases below the pressure supplied by blower.

I34 prior to or after landing of the aircraft and within the 15 minute interval, then the blower I34 will immediately be placed in operation to continue the supply of scavenging air. Should the temperature of the air jacket or plenum chamber exceed the desired safety limit of 170 'F., the safety switch I30 will be opened, thereby breaking the circuit of the holding coil l'3i, thereby stopping the burner and establishing the scavenging period in the same manner as opening the switch 65 with which the switch I30 is in series circuit.

Referring to Fig. 12, a different form of cam and holding means armature and a different circuit arrangement for the fuel pump motor is shown. The operation of this control system and apparatus will be apparent from the above'description, taken in connection with the following. When the timing r'heans motor 200 is set or wound by operation of the key or knob the cam 202 will engage the switch operating follower member 203 to close the main switch 204. Upon continued winding of the motor, the cam 205 will engage the switch operating follower member 206 to actuate the switch arm 201 of the double throw switch 208, thereby breaking circuit at the inlet closed contact 209 and making circuit at the normally open contact 2 l0. Simultaneously with the engagement of cam 202 with follower memher 203, the lost motion pin 2i i will engage the end of the lost motion slot M2 to initiate movement of the cam member 2|3. When the cam member 2l4 carrying cams 202 and 205 has been moved suificiently to carry the cam 202 a distance equal to say twenty minutes of timing motor running time beyond or to the'left of follower member 203, the cam 2| 5 of member 2l3 will engage and move under the cam follower 2l6, thereby to close the switch 2". Simultaneously with closure of switch M1, the holding means armature 2| 8 carried by the cam member 2l3 will be moved into magnetic holding relation relative to the electro-magnet 2l9. Closure of the main switch 204 will complete a circuit from thebattery or current supply source 220 via lead wire 22f to the lead wires 222, 223 leading respectively to the fixed contact of switch 204 and to the switch arm 224 of the relay switch 225. From the closed switch 204 a lead wire 226 connects through the panel terminals to a lead wire 221 connected to the switch arm 228 of combustion air pressure responsive or ram switch 229 and thence through the normally closed contact 230 to the hot wire igniting means 236 as follows: From main switch lead wire 226 via lead wire 231 to switch arm 201 in contact-with a now closed but normally opened contact 2l0, thence via lead wire 230 to one terminal of the coil 235, thence via lead wire 239 to panel terminals and via lead wire 240 to one terminal of the ignition wire 236, and from the other ignition terminal via lead wire 2 to ground. The relay switch 225 is in shunt circuit with the now open, but normally closed, switch contact 209 and closure of relay switch 225 by ener'gizatlon of its coil 235 completes a circuit from the battery 220 through relay arm 224, to relay contact 242, thence via lead wire 243 to low motor speed resistor 244 connected in lead wire'245, which is connected to lead wire 246,

leading to one terminal of the cam operated switch 1. From the other terminal of switch 2| 1, the lead wire 241 connects to panel termipump 255 to the constant level valve 256 which supplies the capillary oil feeding means 251 in the combustion chamber 256 of the heating apparatus 259. Connected to the lead wire 241 from switch 2" there is a lead wire 260 connected to one terminal of the electro-magnet 2l9 from the other terminal of which extends a lead wire 26| to the contact 262 of the burner stopping switch 263, having its switch arm 264 operable by the push button 265. From the arm 264 a lead wire 266 connects to the. panel terminals and a lead wire 26 1 connects to the fixed contact of the bonnet temperature responsive safety switch 266 having its temperature actuated arm connected to ground by lead wire 269. From the foregoing, it will be apparent that the heating apparatus is now in operation, the knob 20! having been released, fuel being supplied by the pump 255 and combustion air. by the blower 233, the combustible mixture being ignited by the hot wire igniter 236,

assuming, of course, that the proper amperage was supplied to the relay coil 235 as above described with Figs. 1 to 11. When the timing means 200 has run for the desired ignition period of five minutes, then the cam 205 will move out from under the follower member 206, so that the switch 200 willbe actuated to break circuit at contact 2l0 and to make contact at 209, the cammember 2l3 being held by electro-magnet 2l9 against the force of the return spring 210 in position with cam 2|5 holding the switch 2i 1 closed by reason of the permitted lost motion between pin 2 and slot 2|2. Closure of switch 206 establishes a circuit from the battery 220 in shunt with the relay switch 225, via a lead wire 21l which connects the contact 209 to the lead wire 245 of the resistor 244. When the cam 205 moves out from under the followermember 206 the end wall of the lost motion slot 212 will be engaged by pin 2| I, thereby stopping further running of the timing means motor 200, and the burner will continue in operation at low fuel consumption as long as the pressure in air supply duct 212 does not exceed the air pressure provided by the blower 233. Breaking of circuit of contact 2|0 deenergizes the relay coil 235 and the hot wire igniter 236. When the aircraft supplied by the heating apparatus 250 is in flight, so that the pressure of the air supplied to duct 212 through the branch duct 213, opening to the exterior of the aircraft, exceeds the pressure provided by the blower 233, then the ram switch 223 will be actuated to break circuit at the contact 230 and to make contact at the normally opened contact 214 so that current will flow from the switch arm 228 through lead wire 215 to the panel terminals and thence via lead wire 216 to the lead wire 240 and cam actuated switch 2" which controls the fuel pump motor 253. Closure of this circuit at contact 214 short circuits the low speed resistor 244 so that the speed of motor 253 will be increased to provide the necessary increased supply of fuel to compensate for the increased air supply due to the higher air pressure in the combustion chamber supply duct 212. Closure of the circuit at ram switch contact 214 also completes the circuit from lead wire 216 through lead wire 211 to the pilot light indicators 218, which is connected to ground. As in connection with Figs. 1 to 11, discontinuance of burner operation is effected by depressing the push button 235 which opens the burner stopping switch 263, thereby deenergizing the holding magnet 219 so that the sprin 210 retracts the cam MS from its position holding switch 2l1 closed and also moves the end wall of slot 212 out of holding relation to the pin 2| 1 so that the timing motor 200 is permitted to continue its operation of returning earn 202 to the position shown in Fig. 12. This time period of reinstated operation of the motor 200 extends over a minute period prior to movement of cam 202 out of holding relation to minimum switch 204, so that during this time period the blower motor 232 will be energized to supply scavenging air to the combustion chamber 258 as the pressure in the duct 212 is below the pressure provided by the blower 233, all as above described in connection with Figs. 1 to 11.

In Fig. 13 there is shown a modification of the fuel supplying means of Figs. 11 and 12. In this Fig. 13 the control of the fuel supply is by means of electrically operated or solenoid valves 280, 28! controlling flow from a manifold or conduit 232 to a pipe or conduit 283 which feeds the fuel distributing means in the combustion chamber. The valve 280 may be connected to the lead wire 124 of Fig. 11 leading from socket terminal B connected to jacket terminal B and controlled by switch 31. The valve 28| may be connected to return wire I26, connected to socket terminal G, which is connected to jacket terminal G having its circuit controlled by cam switch 30 and the air pressure responsive switch 140. Thus, for blower air supply to the combustion chamber the fuel will be fed through valve 280 alone and for flight or high combustion air pressure fuel will be supplied through both of the valves 280 and 28!.

In Fig. 14, the timing motor is electrical and the control device and system is constructed and arranged substantially as above. When it is desired to start the heating apparatus in operation, the control arm 300 is rotated through 120 to the start position, which rotates shaft 30| having fixed thereon a cam disc or member 302 with a main switch operatin cam 303 and a relay and igniter controlling cam 304. The

cm member 302 is coupled to a cam disc or member 303 by a lost motion pin and slot connection 300, such that the shaft 301 is movable relative to the shaft 331 to which the member 305 is fixed. Rotation of shaft "I to the start position first moves cam 303 into operative engagement with the follower member 300 to close the main switch 300. Upon rotation of cam member 302 through substantially from the point of operation of switch 300, the earn 304 engages follower member 310 to actuate the double throw switch 31 I to break contact at the normally closed contact 3l2 and to make contact at the normally open contact 3l3 at the time of closure of switch 303. The lost motion between cam members 302 and 305 is taken up so that the member 305 is rotated with the member 302 and so that upon substantially 30 of shaft rotation upon operation of follower member 310, the cam 3 ofcam member 305 engages its follower member 315 to close the low speed fuel pump switch 316, the high speed fuel pump switch 3H and to open the timing motor switch 3l0. As in the device of Figs. 1 to 11, the rotation of shaft 301 also rotates the holding means armature 3|3 against the force of its return spring 320, so that the armature 3 l 3 is positioned in holding relation to its electromagnet 32 1 upon operation of follower member 3|5 by cam 3l4. Rotation of the starting lever 300 to the start position closes the circuit from the battery or source of current supply 322 to the combustion air blower motor 323, the circuit being from the battery 322 (which is connected to ground) through lead wire 324 to the fixed contact of main switch 303 and from the movable switch contact via lead wire 325, through the normally closed contacts of the combustion air pressure responsive or ram switch 326 and lead wire 32'! to one terminal of the blower motor 323 and from the other blower motor terminal via lead wire 328 to ground. Closure of switch 309 also closes circuit from lead wire 325 via lead 1 wire 329 to the movable contact or switch arm of the double throw switch 3| l engaging the now closed, but normally opened, fixed contact 3l3, thence via lead wire 330 to one terminal of the coil 33| of relay switch 332 and from the other coil terminal via lead wire 333 to one terminal of the hot water igniter 334 having its other terminal connected to ground. Energization of relay coil 33! actuates the relay switch arm 335 to engage the fixed relay contact 336, thereby completing a circuit in shunt with the main switch 303 and the normally closed contact 312 of switch 3. This shunt circuit leads from the battery lead wire 324 via lead wire 331 to the switch arm 335 and thence through contact 330 and lead wire 333 to the movable contact of low speed switch 3| 0 and thence via lead wire 339 to lead wire 340 which is connected to one terminal of the fuel pump motor 34! and contains a variable resistance 342. The other terminal of the fuel pump motor is connected to ground by a lead wire 343. From the lead wire 339 a lead wire 344 connects to one terminal of the coil ma net 32! which has its other terminal connected by a lead wire 345 to the fixed contact 346 of the manual burner stopping switch 341, having an operating rod or push button 348. The switch arm 343 of the switch 341 which is operated by the button 340 is connected by a lead wire 350 to ground. The relay switch 332 also controls the electric timing motor III, the circuit being as follows. l'rom the battery lead wire 324 via 70 lead wire 352 to relay switch arm 353 engaged with switch contact 304 and thence via lead wire 355 to one terminal of the motor 35l and from the other motor terminal via lead wire 356 to ground. The motor 3!" is connected through a reduction gear train 351 to a clutch member 358 cooperable with a friction spring clutch member 359 rigid with the shaft 30L Assuming that the igniter 334 is properly energized as described above in connection with the foregoing systems, the burner will be in operation at low fuel supply and will be supplying heated air to the desired supply'points and the timer motor 35i will be rotating the cam member 302 toward igniter stopping position, the cam member 305 being held against rotation by the, armature N3 and its holding magnet 3.

This low fuel supply operation of the burner will continue as long as the combustion air pressure is not in excess of the pressure supplied by the blower 323. When the combustion air pressure exceeds that supplied by the blower 323, such as will result from the aircraft in flight, then the ram switch 326 will be actuated to break contact between lead wires 325 and 321 and to make contact between lead wire 325 and lead wire 360 leading to the high speed fuel motor switch 3 I 1, which is held closed by the cam 3. From the closed switch 3" current will flow through the lead wire 3H to the adjustable contact 362 of the resistor 342, thereby shunting out a part of the resistor 342 and reducing the resistance in the fuel pump motor circuit which will result in increasing the speed of the fuel pump and accordingly the supply of fuel to the burner. As long as the increased air pressure continues, the increased supply of fuel will continue. When the combustion air pressure decreases to the pressure created by the blower 323, then the ram switch 326 will again place the blower 323 in operation by closure of contact between lead wires 325 and 321, which will also break the circuit through switch 3 so that the fuel pump motor will again be operated at low speed. When it is desired to stop further operation of the burner, irrespective of whether the aircraft is in flight or on the ground, that is, irrespective of the ram switch 326, the manual stopping switch 341 is actuated by the push button 348 which will break the circuit through the holding magnet 32I. Release of the armature 3l9 by the deenergization of magnet 32l will permit spring 320 to rotate cam 3 from its holding relation to follower member 3l5 due to the lost motion pin and slot connection 306. Release of the follower member 3i5 will result in the opening of switches 3 i 6 and 3H, thereby deenergizing the fuel pump motor 34! and will close switch 3l8, thereby completing a shunt circuit to the timing motor 35i as follows:

From the ram switch lead wire 325 through lead wire 363 to the fixed contact of switch M3 and thence through the switch arm via lead wire 364 to the lead wire 355, connected to the timing motor 35i. This will reinstate operation of the motor 35!, thereby reestablishing rotation of cam member 302 to provide a predetermined time period prior to opening of main switch 309 controlling the blower 323. When the motor 35l has operated through a period of say minutes for scavenging of the combustion chamber, either by operation of blower 323 or by the increased pressure of flight created combustion air, then the cam 303 will move out of holding engagement with follower member 300 and switch 303 will be opened. The opening of switch 300 breaks the 14 circuit through switch 3", thereby deenergizing and stopping the timing motor 3 in the stop position of operating or setting knob or handle 300. In Fig. 15 another form of electrically driven timing motor control is shown. In this figure a single operating cam rotatable in one directionv only is employed and the manual reverse cam operation for starting of the heating apparatus is eliminated. When it is desired to start the burner of the heating apparatus in operation, the main switch 400, which is a double throw manual switch having an operating extension or lever 40l operatively connected to its switch arm 402 is moved to the left facing Fig. 15 to engage the switch arm contact with the fixed switch contact 403, so that a circuit from the battery or source of current supply 404 is completed through the lead wire 405 to and through the switch 400 and thence through lead wire 406 to one terminal of the coil 401 of the timing motor controlling relay switch 403. From the other terminal of coil 401, a lead wire 409 extends to the switch arm 0 of a normally closed cam operated switch 41 i. From the fixed contact 2 of the snap acting switch 4 a lead wire 3 connects to one terminal of the hot wire igniting means 4| 4 which has its other terminal connected to round. Operation of switch 400 to close circuit through its contact 43 therefore energizes the igniter 4H and actuates the relay switch 408, provided the igniter circuit is complete and the current supply is suflicient to actuate the relay switch 400 as described above in connection with Figs. 1 to 11. The operation of relay switch 400 pulls the relay switch arm 5 into engagement with the fixed relay contact M6 to close the circuit of the timing motor 1 as follows: From main switch lead wire 406 through lead wire 8, to relay switch arm 5 and its engaged contact 3 to lead wire 3, connected to the closed contact 420 of the normally closed cam operated snap acting switch 4, having its switch arm 422 movable, linked for movement in unison with switch arm 0. From the switch arm 422 a lead wire 423 extends to one terminal of the timing motor 1, which has its other terminal connected to ground by a lead wire 424. Energization of timing motor 1' drives its cam member 425 to move the cam clockwise in the direction of the arrow facing Fig. 15, to move cam 426 out of holding relation to-the cam follower thrust member 421 so that the snap acting switches 428 and 423 are moved to closed position. Closure of the blower control switch 423 completes a circuit to the combustion air supplying blower motor 430 through the combustion air pressure responsive or ram switch 43l as follows: From battery lead wire 405 through lead wire 432 to the fixed contact of switch 420, and from its cam operated switch arm 433 via lead wire 434, to the normally closed contacts of ram switch 43l and therethrough to the lead wire 435 connected to one terminal of the blower motor 430 having 'its other terminal connected to ground by lead wire 436. The main switch 400, upon engagement with its contact 403, also controls the motor of the fuel supply pump 431 through the intermediary of relay switch 430. Engagement of switch arm 402 and contact 403, which closes the circuit from the battery, 404 to lead wire 406, energizes the relay switch coil 43! having one terminal connected'by lead wire 440 to the lead wire 406 and having its other terminal connected to ground by lead wire 4. The cam operated blower switch 420 also controls the energization of the fuel pump motor 431 as it is in series cir.

'411 and of the lgniter 414.

acsaoos with fixed contact 444, thereby completing the circuit to one terminal of the pump motor 421 via lead wire 445 having therein the low speed resistance 446, the other terminal of the pump motor being connected to ground by lead wire 441. The heating apparatus willnow be in operation at low fuel consumption to supply the desired amount of heat in accordance with the combustion or supply provided by the blower. Upon increase in the pressure of the combustion air about the pressure provided by the blower, such as will occur when the aircraft is in flight, the ram switch 421 will break circuit between the blower motor supplying lead wires 434 and 435 and will make circuit from the lead wire to the lead 440 connected to the switch arm 449 of relay switch 438 and movable in unison with the switch arm 442. Since the switch arm 449 is in engagement with fixed relay contact 450, the circuit will be completed from lead wire 448 to the lead wire 451 which connects to the adjustable contact 452 of the resistance 446, thereby shunting out a portion of the resistance 446 to increase the speed of the fuel pump motor 431, in order to provide the necessary quantity of fuel for a proper fuel air mixture with the increased combustion air supply.

The cam member 425 has been rotating at a predetermined rate, preferably a 20 minute cycle, and when the cam 425 has been rotated through 90 it will, at the end of the five minute period, engage the follower thrust member 453 to operate the arms 422 and 410 of the switches 421 and 411 respectively to break the circuit of the timer motor Although the circuit to the timing motor 411 is broken at the relay switch 408 upon opening of switch 411 which deenergizes the relay coil 401, the switch 421 provides a safety control to assure stopping of the timing motor 411 in the event relay switch 405 should fail to open. Upon operation as above described, either at low or high fuel, consumption will not be affected by the time of operation of follower member 453 by cam 425. When it is desired to stop operation of the burner, the switch operating member 401 is moved to the position shown in this Fig. in which switch arm 402 engages the fixed contact 454 so that the timing motor 411 is reenergized from the battery 404 through the following circuit: From switch contact 454, through lead wire 455 to the closed cam switch 429 and thence via lead wire 456 to the timing motor lead wire 423. Accordingly, if dur' ing the interval of reinstated timer motor operation the combustion air pressure has decreased below the predetermined blower pressure at which ram switch 431 remakes circuit between lead wires 434 and 435, the blower motor 430 will again be placed in operation to provide scavenging air for the combustion chamber. Upon the termination of the reinstated operating period of 15 minutes of the timing motor 411, the cam 425 will engage the follower member 421 to open the cam switches 428 and 429 to break the circuits of and stop the blower motor 430 and the timing motor 411 respectively and halting or stopping the cam 426 in its position for the start of another burner heating period when desired.

In Fig. 16 the heating apparatus is shown as having a multi-speed combustion air blower and as having high frequency spark ignition for the combustible fuel and air mixture such as disclosed 16 in my eo-pendlng joint application with Ross E. Scott, Serial No. 478,600 filed March 10, 1943, now Patent No. 2,444,239, granted June 29, 1948. In this form of the invention, the main switch 500 may be a temperature responsive automatic switch having a bimetal operated element 501 for actuating a plurality of switch contacts, namely a low speed contact 502, an intermediate higher speed contact 502 and a high speed contact 504 which are cooperable respectively with fixed contacts 505, 500 and 501. The blade 501 and its contacts are connected to a source of current supply via lead wire 500. Upon demand for heat or operation of the heating apparatus, the contact 502 is moved into engagement with the fixed contact 505, thereby completing a circuit through lead wire 509 to the low motor speed resistor 510 connected to the lead wire 51 1 of one terminal of the combustion air blower motor 512having its other terminal connected by lead wire 512 to the return wire 514 connected to the source of current supply. Operation of the blower 515 by the motor 512 will supply combustion air under pressure through the air supply duct 515 to the combustion chamber 511. The engagement of contacts 502 and 505 will also close the circuit to the coil 510 of relay switch 519 controlling the burner ignition means 520, the coil being energized through lead wire 521 connecting the coil to the lead wire 501 and via the lead wire 522 extending from the coil to the return wire 514. The relay switch 519 is con nected by lead wire 523 to the current supply wire 500 and to one terminal of the primary coil of a current supply transformer 524 by a lead wire 525, the other terminal of the transformer primary coil being connected to the return wire 514 by a lead wire 525. Therefore, the high frequency spark ignition means 520 will be energized simultaneously with the energization of the blower motor 512, with a resulting micro amperage radio frequency high voltage spark discharge from the end or tip 521 of the spark discharge electrode 520. Engagement of contacts 502 and 505 will also energize the motor 529 of the fuel supply pump 530 discharging fuel from a fuel tank not shown to and through the fuel nozzle 531 into the combustion chamber 511, the circuit of motor 520 being as follows: From the lead wire 509 on the switch controlled side of the resistor 510, a lead wire 502 connects to the swi ch arm 533 of a combustion air pressure resposive r will switch 524 having a low speed contact 535, inter mediate higher speed contact 535, and a high speed contact 521. At low combustion air pressure resulting from low blower motor speed, the pressure responsive member 538 of switch 534 will be holding the switch arm 533 in engagement with contact member 535 so that the current supply to the return wire 53! of the pump motor 525 will be through the low speed resistor 540 and from the other motor terminal via lead wire 541 to the return line wire 514. If the temperature should now decrease irrespective of operation of the heating apparatus, the switch 500 will move contact 503 into engagement with contact 5115, thereby shunting the resistor 510 and supplying current to the blower motor 512 from supply line wire 500 through intermediate motor speed resistor 542 to the motor lead wire 511. The increased blower speed resulting from the cutting in of the lower resistance resistor 542 will increase the combustion air pressure and the quantity of air discharging through the duct 515 to the combustion chamber 511, thereby actuating the responsive member 030 of switch I, so as to move switch arm 533 into circuit making engagement with the fixed switch contact 530. This will cut out the resistor in and establish the circuit to the motor lead wire 530 through the intermediate or lower resistance resistor 543, so that the proper ratio of fuel and air increased in quantity per unit of time will be supplied to the combustion chamber 5|! to increase the heat supplied by the heating apparatus. If the contacts 500 and 501 of the switch 500 are now closed as by a further drop in temperature of the ambient medium af-' fecting switch 500, then the resistors 5| and 542 will be shunted by a lead wire connecting the switch contact 501 to the motor lead wire ill, with the result that the lower motor 5l2 will be operated at its highest speed, thereby to further increase the pressure or quantity of air discharged through the duct 5I6 to the combustion chamber 511. This further increased air pressure in the duct 5H3 will act on the switch responsive member 538 to move the switch arm 533 into electrical engagement with the high speed contact 531, so that the resistors 540 and 543 will be shunted out of the circuit of motor 529, the motor now being supplied with current from contact 531 by lead wire 545 to lead wire 539. This increased motor speed will increase th'e speed of the pump 530 so that the fuel supply will be increased in accordance with the increased supply of air through duct 516 in order to provide the desired combustible ratio of fuel to air at a further increased quantity or unit of time, thereby providing a further increased supply of .heat by the heating apparatus. the heating apparatus raises the temperature of the ambient affecting switch 500 so that the contacts 504 and 501 and then the contacts 503 and 506 are separated, that the reverse operation of the burner will occur, cutting down the speed of the fuel pump in accordance with the decreasing It will be apparent that as speed of the blower motor an that when the switch 500 is satisfied and contact 502 is separated from contact 505, that the pump and blower motors will be deenergized and the relay switch 500 will be opened to deenergize the ignition means 520.

It is to be understood that the ignition means of Figs. 16 could be utilized in the control systems of Figs. 1, 12, 14 and 15 if the safety feature of the series circuit arrangement of the relay coil and hot wire igniter were considered unnecessary but that the ignition means 520 of Fig. 16 could be utilized in the systems of Figs. 1 1, 12, 14 and 15 with the safety means disclosed in the above mentioned co-pending application as another method of accomplishing the assurance of proper ignition means operation.

What is claimed and is desired to be secured by Letters Patents of the United States is:

1. A heatingapparatus comprising a combustion chamber, means to supply fluid fuel to said chamber, a circuit for said means, electric ignition means for the fuel supplied to said chamber, a circuit for said ignition means, a relay switch having a coil in circuit with said ignition means, electromagnetic holding means having an armature and having a coil, a circuit for said holding means coil and controlled by said relay switch, a switch controlling the circuit of said ignition means and said relay coil, a switch in circuit with said relay switch to control said holding means coil, said last-named switch being movable with said armature and controlling the circuit of said fuel supply means, means to close said relay coil 18 controlling switch, and means operated by said last-named means to close said fuel supply switch and to move said armature into holding relation to said holding means coil.

2. A heating apparatus comprising a combustion chamber, means to supply fluid fuel to said chamber, a circuit for said means, electric ignition means for the fuel supplied to said chamber, a; circuit for said ignition means, a relay switch having a coil in circuit with said ignition means, electro-magnetic holding means having an armature and having a coil, a circuit for said holding means coil and controlled by said relay switch, a switch-controlling the circuit of said ignitionfmeans and said relay coil, a switchin circuit with said relay switch to control said holding means coil, said last-named switch being movable with said armature and controlling the circuit of said fuel supply means, means to close said relay coil controlling switch, means operated by said last-named means to close said fuel supply. switch and to move said armature into holding relation to said holding means coil, means tending to move said fuel supply switch to open position, and means to deenergize said holding, means for operation of said fuel supply switch by said tending means.

tion'chamber, means to-supply fluid fuel to said chamber, a circuit for said means, means to supply combustion air under pressure to said chamber, a circuit for said air supply means, electric ignition means for the fuel supplied to said chamber, a circuit for said ignition means, a relay switch having a coil in circuit with said ignition means, electro-magnetic holding means having an armature and having a coil, a circuit for said holding means coil and controlled by said relay switch, a switch controlling the circuit of said air supply means, a switch controlling the circuit of said ignition means and said relay coil, a switch in circuit with said relay switch to con-' trol said holding means coil, said last-named switch being movable with said armature and controlling the circuit of said fuel supply means, means to close said air supply switch and said relay coil controlling switch, and means operated by said last-named means to close said fuel supply switch and to move said armature into holding relation to said holding means coil.

4. A heating apparatus comprising a combustion chamber, means to supply fluid fuel to said chamber, a circuit for said. means, means to supply combustion air under pressure to said chamber, a circuit for said air supply means, electric ignition means for the fuel supplied to said chamber, a circuit for said ignition means, a relay switch having a coil in circuit with said ignition means, electro-magnetic holding means having an armature and having a coil, a circuit for said holding means coil and controlled by said relay switch, a switch controlling the circuit of said air supply means, a switch controlling the circuit of said ignition means and said relay coil, a switch in circuit with said relay switch to control said holding means coil,

said last-named switch being movable with said 19 supply switch and to move said armature into holding relation to said holding means coil,

5. A heating apparatus comprising a combustion chamber. means to supply fluid fuel to said chamber, a circuit for said means, means to supply combustion air under pressure to said chamber, a circuit for said air supp y means, electric ignition means for the fuel suppliedto said chamber, a circuit for said ignition means, a relay switch having a coil in circuit with said ignition means, electro-magnetic holding means having an armature and having a coil, a circuit for said holding means coil and controlled by said relay switch, a switch controlling the circuit of said air supply means, a switch controlling the circuit of said ignition means and said relay coil, a switch in circuit with said relay switch to control said holding means coil, said last-named switch being movable with said armature and controlling the circuit of said fuel supply means, a settable timing means, drive means operated upon setting of said timing means to start a heating cycle and acting to close said air supply switch and said relay coil controlling switch, and means operated upon setting of said timing means to close said fuel supply switch and to move said armature into holding relation to saidholding means coil. said timing means acting upon operation to actuate said drive means to open said ignition controlling switch.

6. A heating apparatus comprising a combustion chamber, means to supply fluid fuel to said chamber, a circuit for said means, means to supply combustion air under pressure to said chamber, a circuit for said air supply means, electric ignition means for the fuel supplied to said chamber, a circuit for said ignition means, a relay switch having a coil in circuit with said ignition means, electro-magnetic holding means having an armature and having a coil, a circuit for said holding means coil and controlled by said relay switch, a switch controlling the circuit of said air supply means, a switch controlling'the circuit of said ignition means and said relay coil, a switch in circuit with said relay switch to control said holding means coil, said last-named switch being movable with said armature and controlling the circuit of said fuel supply means, a settable timing means, drive means operated upon setting of said timing means for the start of a heating cycle and acting to close said air supply switch and said relay coil controlling switch, and means operated upon said setting of said timing means to close said fuel supply switch and to move said armature into holding relation'to said holding means coil, said timing means acting upon operation to actuate said drive means to open said ignition and relay coil controlling switch, means controlled by said holding' means to stop operation of said timing means following switch opening actuation by said drive means, means tending to open said fuel supply switch and to move said armature out of said holding relation, and means to deenergize said holding means coil.

'7. A heating apparatus comprising a combustion chamber, means including a blower for supplying air under pressure to said chamber, electrically controlled means to supply fuel at different rates of flow to said chamber, a circuit for said electrically controlled means, electrical ignition means for the fuel supplied to said chamber, a circuit for said ignition means, a relay switch having its coil in circuit with said ignition means, a switch controlling the circuit 20 of said coil, means responsive'to an increased pressure of the air supplied to said chamber, means operated by said responsive means and controlling said electrically controlled means to increase the rate of fuel supply to said chamber, switch means controllingthe energization of said first-named circuit, and electrically operated means for maintaining closure of said switch means and including a circuit controlled by said relay switch.

8. A heating apparatus for aircraft comprising a combustion chamber having an air inlet, a

blower for supplying air to said inlet, a circuit for said blower, a duct leading to the exterior of the aircraft for supplying air to said inlet by flight created air pressure, means to supply fuel to said chamber at a low rate and at a higher rate, high rate and low rate circuits for said fuel supply means, electric ignition means for the fuel supplied to said chambena circuit for said ignition means, a switch controlling the circuits of said zs s'ponsive to current flow therethrough so that said relay switch will close only upon flow of sufllcient current to energize said ignitionmeam for ignition of fuel, said relay switch controlling said low rate fuel supply circuit, a pressure switch responsive to air pressure in said duct and controlling said-high rate fuel supply circuit to supply fuel at said higher rate upon the occurrence of a high air pressure in said duct, switch means for I controlling current flow to said fuel supply means circuits, and holding means energized by closure of said relay switch and operable to control said switch means and said first-named switch.

9. A heating apparatus comprising a combustion chamber having an air inlet, electric ignition means in said chamber. a circuit for said ignition means, a relay switch having its coil in circuit with said means, a switch controlling the circuit of said coil and said ignition means, fuel supply means for said chamber, a circuit for said 'fuel supply means and controlled by said relay switch, electro-magnetic holding means having an armsture and having a coil, a circuit for said holding means coil and controlled by said relay switch, a switch in circuit with said relay swltchiand'controlling the circuits of said holding means coil and said fuel supply means, means operableto'close' said last-named switch and to move said armature into holding relation to said holding'means coll, means overcome by the force of said holding means coil and tending to move said armature away from said holding means coil and to move said last-named switch to open position, a manually wound timing motor, means operable upon winding of said motor to close saidv relay coil H controlling switch, lost-motion means connecting said last-named means andsaid armature oper-' ating means so that said timing motor can operate sald last-named means while said armature is held by said holding coil, said holding coil acting through said lost-motion means to hold said timing motor against operation upon movement of said relay coil controlling switch to open position by said timing motor, and means to deenergize said holding coil to release said armature and said timing motor.

10. A heating apparatus comprising a combustion chamber, a blower for supplying air to said chamber, a circuit for said blower, electrically operable means for supplying fuel to said chamber, a circuit for said means, hot wir ignition means in said chamber, a circuit for said ignition means, a main switch controlling the circuits of said blower and said fuel supply means, a double throw switch having a first position with normally closed contacts controlling the circuit from said main switch to said fuel supply means. arelay switch shunting said normally closed contacts and having an operating coil in circuit with said ignition means, said double throw switch in said first position having normally open contacts controlling current flow to said relay operating coil and said ignition means, electro-magnetic holding means having a coil and an armature, a circuit for said holding means coil, "'8, switch controlling the circuit of said holding means coil and the circuit of said fuel supply means, a settable timing motor having a predetermined running time, a plurality of cams movable by setting of said motor, two of said cams being movable in unison and being operable respectively upon setting of said motor first to close said main switch and then to actuate said double throw switch to close said normally open contacts and to open said normally closed contacts, a third one of said cams being movable with said armature and acting at the limit of setting of said motor to close said holding means 0011 switch, means opposing movement of said third cam to close said holding means coil switch, said armature at said limit being moved against the force of said opposing means and into holding relation to said holding means coil, means to stop said motor upon cam operation of said double throw switch to said first position to break the circuit of said ignition means, and means to deenergize said holding means to reinstate operation of said two cams by said timing motor and to release said opposing means to actuate said third 'cam to deenergize said fuel supply means.

A 11. A heating apparatus comprising a combustion chamber, a blower for supplying air to the circuit of said fuel supply means and having an operating coil in circuit with said ignition means, a switch controlling the circuit of said operating coil and said ignition means, a switch in shunt with said relay switch, a cam driven by said motor and operable upon a predetermined lapse of time to close said shunt switch and to open said operating coil and ignition means switch, a fuel supply means stopping switch in circuit with said shunt switch and said relay switch, a cam controlled by said motor and operable to hold said stopping switch closed,

' timing means, a relay switch controlling the cirelectro-magnetic holding means operable to hold manually set timing motor, a cam driven by said motor and operable to open said main switch, electrically energized fuel supply means for said chamber, a circuit for said fuel supply means, hot wire ignition means in said chamber, a circuit for said ignition means, a relay switch controlling the circuit of said fuel supply means and having an operating coil in circuit with said ignition means, a switch controlling the circuit of said operating coil and said ignition means, a switch in shunt with said relay switch, a cam driven by said motor and operable upon a predetermined lapse of time to close said shunt switch and to open said operating coil and ignition means switch, a fuel supply means stopping switch in circuit with said shunt switch and said relay switch, a cam movable relative to said firstnamed and said second-named cams and controlled by said motor and operable to hold said stoppin switch closed, electro-magnetic holding means operable to hold said last-named cam against movement uponoperation of said motor, a circuit for said holding means, said cams being operated upon setting of said motor and being so constructed and arranged that said firstnamed cam closes said main switch to start said blower, then said second-named cam opens said shunt switch and closes said operating coil and ignition switch, and finally said third-narned cam closes said stopping switch, means operable to stop said motor upon motor operation of said shunt and ignition means switches by said second-named cam, and a switch to break the circuit of said holding means thereby to stop operation of said fuel supply means.

13. In a heating apparatus, electrically energized fuel supply means, a circuit for said means,

hot wire ignition means for the supplied fuel, a circuit for said ignition means, manually settable cuit to said supply means and having its coil in series circuit with said ignition means, a main switch controlling the circuit of said coil and the circuit of said supply means, a second switch having normally closed contacts shunting said relay switch and having normally open contacts in series circuit with said coil, a cam driven by said timing means and operable upon setting of said timing means to open said normally closed contacts and to close said normally open contacts so that said relay switch will energize said fuel supply means, said cam acting upon predetermined running of said timing means to open said normally open contacts and to close said normally closed contacts thereby to maintain said supply means energized, and means to stop the running of said timing means upon opening of said normally open contacts.

14. In a heating apparatus, electrically ener-- gized fuel supply means, a circuit for said means, hot wire ignition means for the supplied fuel, a

circuit for said ignition means, manually settable series circuit with said .coil, a cam driven by said timing means and operable upon setting of said.

timing means to open said normally closed contacts and to close said normally open contacts so that said relay switch will energize said fuel supply means, said cam acting upon predetermined running of said timing means to open said normally open contacts and to close said normally amen closed contacts thereby to maintain said supply means energized, means to stop the running of said timing means upon opening of said normally open contacts, an electrically driven blower for supplying air for combustion, a circuit for said blower, said main switch controlling the circuit of said blower, a cam operable to close said main switch upon setting of said timing means, said last-named cam being driven by said timing means and operable upon predetermined running of said timing means to open said main switch thereby to stop said blower, a switch controlling the circuit of said fuel supply means, and means operable upon opening of said last-named switch to restart running of said timing means thereby to determine the duration of operation of said blower subsequent to opening of said last-named switch.

15. A heating apparatus comprising a combustion chamber, a duct for supplying combustion air to said chamber, a blower having a motor and for supplying air under pressure to said duct, a

circuit for said motor, said duct having an opening for admission of air at greater pressure to said chamber than the pressure supplied by said blower, a pump for supplying fuel to said chamber, a multi-speed motor for driving said pump, said pump motor having a low speed for-supplying fuel in accordance with the air supplied by said blower and having a higher speed for supplying fuel in accordance with the greater air pressure, circuits for said pump motor, a hand wound timing motor, a shaft driven by said timing motor, a second shaft driven by and having lost motion relative to said first-named shaft, a plurality of cams fixed on said first-named shaft, a normally open main switch controlling the circuit of said blower motor and controlled by one of said cams, a hot wire ignition means in said combustion chamber, a circuit for said ignition means, a

relay switch controlling the low speed circuit of said pump motor and having its relay coil in series circuit with said ignition means, a doublethrow switch controlled by another of said cams and having normally closed contacts in shunt with said relay switch and having normally open contacts controlling the circuit to said relay coil, a pump motor cam fixed on said second shaft, a .pair of normally open switches controlled by said pump motor cam, one of said pair of switches being in series circuit with saidnormally closed contacts of said double-throw switch and with said relay switch, the other of said pair of switches controlling the higher speed circuit of said pump motor, a pressure actuated doublethrow switch responsive to pressure in said duct and having normally closed contacts controlling the circuit of said blower motor and having normally open contacts in series circuit with said.

other of said pair of switches, a holding magnet, a circuit for said holding magnet and controlled by said one of said pair of switches and by said relay switch, an armature cooperable with said magnet and rigid with said pump motor earn, a spring resisting movement of said armature into holding relation to said magnet, said one cam acting upon initial winding of said timing motor to close said main switch, said other cam acting to operate said first-named double-throw switch for predetermined operation of said ignition means upon running of said timing motor, said pump motor cam acting to close said pair of switches, said magnet acting through said holding magnet circuit being controlled by said relay 24 switch during said predetermined ignition means operation, saidsecond shaft at the limit of lostmotion'of said second shaft to stop the running of said timing motor and acting through said armature and said pump motor cam to maintain said pair of switches closed for energization of said high speed pump motor circuit, and a normally, closed stopping switch in the circuit of said magnet for deenergizing said magnet to release said timing motor for operation and to release said pump motor cam for opening of saidpair of switches.

16. A heating apparatus comprising a combustion chamber, a duct for supplying combustion air to said chamber, a blower having a motor and for supplying air under pressure to said duct, a circuit for said motor, said duct having an opening for admission of air at greater pressure to said chamber than the pressure supplied by said blower, a pump for supplying fuel to said chamber, a multi-speed motor for driving said pump, said pump motor having a low speed for supplying fuel in accordance with the air supplied by said blower and having a higher speed for supplying fuel in accordance with the greater air pressurejcircuits-for said pump motor, a hand wound timing motor, a shaft driven by said timingmotor, a second-shaft driven by and having lost motion relative to said first-named shaft, a plurality of cams fixed on said first-named shaft, a normally open main switch controlling the circuit of said blower motor and controlled by one of said cams, a hot wire ignition means in said combustion chamber, a circuit for said ignition means, a relay switch controlling the low speed circuit of said pump motor and having its relay coil in series circuit with said ignition means, a double-throw switch controlled by another. of said cams and having normally closed contacts in shunt with said relay switch and having normally opeu con'tacts controlling the circuit to saidrelay coil, a resistance for low speed pump motor operation in series circuit with said relay switch and said normally closed contacts of said double-throw switch, a pump motor cam fixed on said second shaft, a normally open switch means arranged for closure by said pump motor cam and in and controlling said high speed pump motor circuit, a pressure actuated doublethrow switch responsive to pressure in said duct and having normally closed contacts controlling the circuit of said blower motor and having normally open contacts in shunt circuit with said resistance and said normally closed contacts of said double-throw switch, a holding magnet, a

circuit for said magnet and controlled by said running of said timing motor, said magnet acting through "said second shaft at the limit of lostmotion of said second shaft to stop the running of said timing motor and acting through said armature and said pump motor cam to maintain said normally open switch means closed for energization of said high speed pump motor circuit,

and a normally closed stopping switch in the circuit of said magnet for deenergizing said magnet to release said pump motor cam' for opening of its normally open switch means to stop said pump motor, said relay switch controlling said holding magnet circuit during said predetermined ignition means operation.

17, A heating apparatus comprising a combustion chamber, a duct for supplying combustion air to said chamber, a blower having a motor and for supplying air under pressure to said duct, a circuit for said blower motor, said duct having an opening for admission of air at greater pressure to said chamber than the pressure supplied by said blower, a pump for supplying fuel to said chamber, a multi-speed motor for driving said pump, said pump motor having a low speed for supplying fuel in accordance with the air supplied by said blower and having a higher speed for supplying fuel in accordance with the greater air pressure, circuits for said pump motor, an electrically driven timing motor, a shaft driven by said timing motor, an automatic clutch connecting said timing motor to said shaft, asecond shaft driven by and having lost motion relative to said first-named shaft, a plurality of cams fixed on said first-named shaft, a normally open main switch controlling the circuit of said blower motor and controlled by one of said cams, a hot wire ignition means in said combustion chamber, a circuit for said ignition means, a relay switch switch during said predetermined ignition means controlling the circuit of said timing motor and the low speed circuit of said pump motor and having its relay coil in series circuit with said ignition means, a double-throw switch controlled by another of said cams and having normally closed contacts in shunt with said relay switch and having normally open contacts controlling the circuit to said relay coil, a pump motor cam fixed on said second shaft, a pair of normally open switches controlled by said pump motor cam, one of said pair of switches being in series circuit with said normally closed contacts of said double-throw switch and with said relay switch, the other of said pair of switches controlling the higher speed circuit of said pump motor, a pressure actuated double-throw switch responsive to pressure in said duct and having normally closed contacts controlling the circuit of said blower motor and having normally open contacts in series circuit with said other of said pair of switches, a holding magnet, a circuit for said holding magnet and controlled by said one of said pair of switches and by said relay switch,

an armature cooperable with said magnet and rigid with said pump motor cam, a spring resisting movement of said armature into holding relation to said magnet, said one cam acting upon initial winding of said timing motor to close said main switch, said other cam acting to operate said first-named double-throw switch for predetermined operation of said ignition means upon running of said timing motor, said pump motor cam acting to close said pair of switches, said holding magnet acting through said armature and said pump motor cam to maintain said pair of switches closed for energiztion of said high speed pump motor circuit, a normally closed timing motor switch in series circuit with said main switch and controlled by said pumpmotor cam, and a normally closed stopping switch in the circuit of said magnet for deenergizing said magnet to release said timing motor for operation and to release said pump motor cam for opening of said pair of switches and closure of said 30.!-

operation.

'18. A burner controlling apparatus comprising a hand wound timing motor, electrically operated fuel supply means, a circuit for said means, a hot wire ignition means, a circuit for said ignition means, a relay switch controlling the circuit to said fuel supply means and having a coil in series with said ignition means, a switch closed by winding of said timing motor and controlling the circuit of said coil so that operation of said relay switch is dependent upon operation of said ignition means, and a switch closed by operation of said timing motor for maintaining said fuel supply means energized upon opening of said coil circuit controlling switch by said timing motor.

19. A burner controlling apparatus comprising a hand wound timing motor, electrically operated fuel supply means, a circuit for said means, a hot wire ignition means, a circuitfor said ignition means, a relay switch controlling the circuit to said fuel supply means and having a coil in series with said ignition means, a switch closed by winding of said timing motor and controlling the circuit of said coil so that operation of said relay switch is dependent upon operation of said ignition means, a switch closed by operation of said timing motor for maintaining said fuel supply means energized upon opening of said coil circuit controlling switch by said timing motor, an electrically driven blower for supplying combustion air, a circuit for said blower, a switch closed to start said blower upon winding of said motor, means to stop said motor upon opening of said coil circuit, a switch for deenergizing said fuel supply means, and means to start said motor upon operation of said last-named switch thereby to determine the duration of operation of said blower subsequent to operation of said last-named switch.

20. A heating apparatus comprising a combustion chamber, means for supplying air at low and at high pressures to said chamber and including a blower, a circuit for said blower, electrically controlled means for supplying fuel at low and at high rates of flow to said chamber, a low rate controlling circuit for said electrically controlled means, a high rate controlling circuit for said electrically controlled means, means to close said blower circuit and said low rate circuit, a switch in said low rate circuit and biased to open position, a switch in said high rate circuit and biased to open position, electrically energized holding means for maintaining said switches closed, a circuit for said holding means, a relay switch having an operating coil and controlling said holding means circuit, means'responsive to the high air pressure, means operated by said responsive means to :close said high rate controlling circuit to supply fuel to said chamber at the high rate of fuel flow, a circuit for said operating coil, a hot wire igniter in said chamber and in said operating coil circuit so that upon failure of said igniter said relay switch will Open said holding coil circuit thereby to open said high rate circuit switch and said low rate circuit switch.

21. A heating apparatus comprising a combustion chamber, means to supply fluid fuel at different rates to said chamber, high and low fuel supply circuits for said means, electric ignition means for the fuel supplied to said chamber, a circuit for said ignition means, a relay switch having a coil in circuit with said ignition means,

27 electro-magnetic holding means having an armature and having a coil, a circuit for said holding means coil and controlled by said relay switch, a switch controlling the circuit of said ignition means and said relay coil, switch means in cir- I cuit with said relay switch to control said holding means coil, said last-named switch means being movable with said armature and controlling the circuits of said fuel supply means, means to close said relay coil controlling switch, means operated by said last-named means to close said fuel supply switch means and to move said armature into holding relation to said holding means coil, means controlling said high and low fuel circuits and operable to close said high fuel circuit to increase the supply of fuel by said fuel supply means, and said relay switch controlling the completion of said high fuel circuit by said lastnamed means.

FRED B. AUBERT.

28 nmnsncas crrnn The following references are of record in the me of this patent:

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